Animal studies have demonstrated the ability to influence the development of refractive error by placing the peripheral image field in front of or behind the retina while the central image field is accurately focused. Corneal reshaping to reduce the amplitude of myopia, by increasing the radius of curvature of the central cornea while leaving the peripheral curvature unchanged, has demonstrated the ability to reduce or halt the progression of myopia. The mechanism is understood to be the placement of the peripheral image field in front of the retina while the central image field is accurately focused on the retina.
Emerging myopia or incipient myopia is characterized as a stage in refractive error development when the eye is shifting from greater hyperopia to less hyperopia or when the eye is shifting from emmetropia to myopia. Longitudinal studies of human populations reveal the onset of emerging myopia as early as the age of six. Corneal refractive therapy or overnight corneal reshaping is effective for the temporary reduction of myopia and appears to be effective in regulating the axial length growth of eyes treated for myopia. The current lens designs are intended to increase the radius of curvature of the central cornea and are not indicated for treatment of emerging myopia where the desired treatment would not increase the radius of curvature of the central cornea, for example, where there is a need to decrease the radius of curvature of the mid peripheral cornea.
The prior art teaches the methods of reshaping the central cornea to correct refractive error. For the treatment of myopia, the central corneal radius is increased by way of applying a lens having a central radius of curvature longer than the pre-treated central corneal radius. In the prior art, the mid peripheral cornea is found to remain substantially unchanged during treatment.
For example, prior art contact lens corneal reshaping for the temporary reduction of refractive error utilizes lenses wherein the central zone of the lens is referred to and recognized as the treatment zone. The intention of the prior art is to change the shape of the central cornea in an amount required to reduce the refractive error to a negligible amplitude. If, for example, the pre-treatment refractive error is −3.00 D, or three diopters of myopia, the treatment goal would be to increase the radius of curvature of the central cornea the required length to reduce the power of the cornea by 3.00 diopters. There is no known practice or teaching that suggests any intention to reshape the mid peripheral cornea.